Chemistry 18.1

1. Chemistry 18.1

2. Rates of Reaction 18.1 • The heat given off by the corrosion reaction of an iron-magnesium alloy with salt water can produce a hot meal. The rate of reaction is increased by adding salt water, so heat is produced rapidly. You will learn some ways in which the rate of a reaction can be increased.

3. 18.1 Collision Theory • Collision Theory • How is the rate of a chemical change expressed?

4. 18.1 Collision Theory • In chemistry, the rate of chemical change, or the reaction rate, is usually expressed as the amount of reactant changing per unit time.

5. 18.1 Collision Theory • A rate is a measure of the speed of any change that occurs within an interval of time.

6. 18.1 Collision Theory • Rates of chemical reactions are often measured as a change in the number of moles during an interval of time.

7. 18.1 Collision Theory • According to collision theory, atoms, ions, and molecules can react to form products when they collide with one another, provided that the colliding particles have enough kinetic energy.

8. 18.1 Collision Theory • Effective Collision

9. 18.1 Collision Theory • Ineffective Collision

10. 18.1 Collision Theory • The minimum energy that colliding particles must have in order to react is called the activation energy.

11. 18.1 Collision Theory • An activated complex is an unstable arrangement of atoms that forms momentarily at the peak of the activation-energy barrier. • The activated complex is sometimes called the transition state.

12. 18.1 Factors Affecting Reaction Rates • Factors Affecting Reaction Rates • What four factors influence the rate of a chemical reaction?

13. 18.1 Factors Affecting Reaction Rates • The rate of a chemical reaction depends upon temperature, concentration, particle size, and the use of a catalyst.

14. Factors Affecting Reaction Rates • Animation 22 • Explore several factors that control the speed of a reaction.

15. 18.1 Factors Affecting Reaction Rates • Temperature • Storing foods in a refrigerator keeps them fresh longer. Low temperatures slow microbial action.

16. 18.1 Factors Affecting Reaction Rates • Concentration • a. In air, a lighted splint glows and soon goes out. • b. When placed in pure oxygen (higher oxygen concentration), the splint bursts into flame.

17. 18.1 Factors Affecting Reaction Rates • Particle Size • The minute size of the reactant particles (grain dust), and the mixture of the grain dust with oxygen in the air caused the reaction to be explosive, destroying the grain elevator.

18. 18.1 Factors Affecting Reaction Rates • Catalysts

19. Factors Affecting Reaction Rates • Simulation 23 • Explore the effects of concentration, temperature, and a catalyst on reaction rate.

20. 18.1 Factors Affecting Reaction Rates • An inhibitor is a substance that interferes with the action of a catalyst. Antioxidants and antimicrobials used in drying fruits and preserving fruit juices slow the action of microbes and limit contact with air.

21. 18.1 Section Quiz. • 18.1.

22. 18.1 Section Quiz. • 1. The units below that would be appropriate to measure the rate of a chemical reaction is • mmol/s. • mol/L. • kJ/mol. • h/mol.

23. 18.1 Section Quiz. • 2. In a chemical reaction, the energy of reactants is always • greater than the energy of the products. • more than the activation energy. • less than the activation energy. • less than the energy of the products.

24. 18.1 Section Quiz. • 3. An increase in which one of the following will NOT increase the reaction rate? • temperature • concentration of reactants • total mass of reactants • surface area of reactants

25. 18.1 Section Quiz. • 4. A catalyst works because it • lowers the activation energy. • increases the temperature. • is permanently changed in a reaction. • supplies energy to a reaction.

26. END OF SHOW